Automatic cigarette processing (manufacturing and/or packing) machines comprise a number of successive work stations, each for performing a sequence of operations by means of the combined action of respective operating devices. By way of example, the operating devices of a work station may comprise a product conveyor powered by a respective electric motor; a gumming device; folding members activated mechanically by the product conveyor (typically using cams) or by respective electric actuators; and a number of sensors for controlling both product quality and machine efficiency.
Known automatic cigarette processing machines comprise a central control unit for controlling the operating devices at the various work stations by means of a number of controllers, each for controlling all the machine operating devices performing the same (or similar) functions. For example, known automatic cigarette processing machines of the above type comprise a central control unit having a PLC or PC processor (so-called machine controller) for performing the machine application program and logic tasks on digital and analog signals (from the various sensors), one or more motion controllers for synchronized-motion functions, and one or more special high-speed-processing controllers.
Automatic cigarette processing machines of the above type pose several drawbacks. Using a number of controllers, each for controlling all the machine operating devices performing the same (or similar) functions, calls for a large number of electric cables along the whole length of the machine to connect each operating device to the respective controller. Moreover, testing the efficiency of each work station (e.g. when assembling the machine) is extremely difficult, on account of each controller being designed to operate simultaneously with all the work stations on the machine. Each controller operates according to a specific logic and employs a specific programming language, which are normally different from those of the other controllers (e.g. PLC""s are programmed in IEC 1131-3 standard object language, whereas motion controllers are programmed in xe2x80x9cCxe2x80x9d language), so that control software development and testing are expensive, painstaking jobs requiring variously skilled programmers. Finally, to increase processing power, one or more of the controllers must be replaced with higher-performance models, thus resulting in relatively high updating costs.
WO0016647 discloses a cigarette manufacturing machine of the aforementioned type, i.e. comprising a central control unit for controlling the operating devices at the various work stations by means of a number of controllers, each for controlling all the machine operating devices performing the same (or similar) functions. In particular the cigarette manufacturing machine disclosed by WO0016647 comprises a tobacco rod maker for making double length tobacco rods, a tipper for applying filters to tobacco rods to form filter tipped cigarettes, and a transfer apparatus for transferring double length tobacco rods from the rod maker to the tipper. Each of the tipper and the rod maker comprises a plurality of field devices for monitoring and/or affecting parameters of the rod maker, the tipper or the cigarettes being manufactured. A motion controller controls a plurality of synchronized motors. A PC based controller controls the motion controller, the devices on the tipper and the rod maker and communicates with an HMI which is running on the same or a separate PC. The devices and the controller are linked by a field bus. The HMI PC and the motion controller are connected to the system controller either over their own links or via the fieldbus.
U.S. Pat. No. 5,787,002 discloses a control system for controlling a production facility, including a plurality of work stations each of which is provided with an automatically controllable working apparatus, has a control device for controlling the working apparatus so as to perform specified working and a data communications network through which the control means communicates data on operation of the working apparatus with other work stations so as to reflect the data in operation of each working apparatus.
DE4217473 discloses a flexible manufacturing system having a loading point for either components or raw materials and an unloading point for the finished products; components are transferred onto a loop conveyor that serves a number of workstations positioned around the outer loop and identification markings are read by local sensor and the data interpreted to select the workstation. Each workstation has a dedicated computer for control purposes and these are in communication with a host computer managing the production control.
It is an object of the present invention to provide an automatic cigarette processing machine designed to eliminate the aforementioned drawbacks, and which at the same time is cheap and easy to produce.
According to the present invention, there is provided an automatic cigarette processing machine comprising a control unit and a number of successive work stations, each having a respective number of operating devices; characterized in that, for each work station, the control unit comprises at least one respective controller directly connected to the work station and for controlling all the operating devices at the work station.